The speed is mentioned in kilometers per hour but the difference is mentioned in seconds. So we convert speed into kms per second by dividing 75 by 3600

Since Speed = distance/time or time = distance/speed (distance is 1 kms) we have time = 1/(75/3600) or t = 48 seconds.

Since the car takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 75 kilometers per hour. we have t = 48 + 2 = 50 seconds.

Now speed = distance/ time. First we convert time of 50 seconds in hours by divding by 3600 to get 50/3600

Therefore speed = 1/(50/3600) = 3600/50 = 72 (Ans B)

_________________

"Please hit +1 Kudos if you like this post"

_________________

Manish

"Only I can change my life. No one can do it for me"